As the Vancouver Marathon approaches I’ve kept an eye on the 10 day forecast, not so much for any inclement weather on race day (Vancouver’s climate is mild and chances are good it’ll be clear), but to monitor the likely temperature. This marathon will already be difficult enough on its own, but the effect of any excessive heat will magnify multifold as I enter uncharted territory in the later miles.
The forecast already called for mostly clear skies and temps over 60, but as days pass the forecasted high temp for race day has grown and now sits at 71’F. The forecasted temp at gun time is currently 60’F, and given my anticipated pace I will likely finish during the 12pm-1pm hour, right as the heat begins to peak.
The London Marathon felled countless runners not too long ago as temps reached 73’F, and not a few people scoffed at runners collapsing in a temperature we’ve been so conditioned to believe is perfectly comfortable that we set thermostats there as a default. Such opinions are clearly the product of people who don’t run regularly.
A key reason we’re advised to dress in winter as if it’s 20 degrees warmer is because your core temperature while running will increase to a point where it feels at least 20 degrees warmer. This remains to some degree true once the weather warms up, and greatly exacerbates the effect of outdoor heat.
You are after all elevating your heart rate and burning about 90-120 calories per mile… and your body when in continuous motion produces heat. Cold can feel normal. Normal feels hot. And any temperature above normal can get dangerously hot.
The standard ideal temperature has been posited at around 50-55 degrees, though I find the ideal overall range for running is between 40 and 60 degrees. Jonathan Savage posits that outdoor temps can begin to slow you down from heat at as little as 50 degrees (you can see the calculated effect here). And of course, the bigger you are the better your body retains heat, which while great in a Chicago winter can feel brutal during a run in warmer weather. (It’s one of a bunch of reasons I worked on losing weight in recent years)
I recall running the Soldier Field 10 last year, and even though the temperature never got above 62, I began to feel overheated in the later miles. Pacing and other factors (plus the distance at the time) may have contributed, but I do recall feeling substantially hotter at the end than past races. I felt weak at the time for having been so affected by such seemingly mild temperatures, especially when racing calculators like the Daniels Tables indicate that’s barely above the threshold (60 degrees) at which heat begins to affect you.
Looking back now, knowing that heat can begin to affect you at 50 degrees, I now realize that I wasn’t too far out of line. If we follow the winter wear 20 degree postulate, my body by that point probably felt like it was about 80-85 degrees outside.
It’s little wonder that at last September’s Great Race 10K in Pittsburgh, where temperatures reached a race-historical high of 87, runners were collapsing and required medical attention at the finish line. I ran that race and had to physically stop between aid stations around mile 4 to avoid illness myself. I finished, but I passed many EMTs attending to fallen runners towards the end, and even watched another runner collapse to the ground amidst more EMTs at the finish line. For all of us racing, that 87 degree temperature felt a lot more like 105-110 degrees as we reached the finish.
What’s beautiful weather for a bystander can be dangerously hot weather for a runner. That 60 degree start time temp at Vancouver may or may not feel hot when we start. But by hour 2, the likely 65 degree temps will feel more like 85-90, and it’s going to get worse as we enter the 10K marathon badlands of miles 20-26 (or for Canadians, kilometers 32-42). As the temps hit 70, it’s going to feel like 90, and if they run out of water in Stanley Park it’s going to get real bad for slower runners.
So now my race planning requires another wrinkle. Never mind making sure I properly fuel and pace myself. I now need to figure contingencies for hydration in the later miles, just in case the compounding effects of marathon exhaustion and heat make the difficult potentially unworkable. Because the latter portion of the race will be at noon, there won’t be much shade as the sun will be directly overhead. And, because the later miles are along the Stanley Park Seawall, it’s not particularly easy to drop out if you must.
I know for sure I’m bringing a water bottle, along with taking liquid at all the available aid stations. The best plan will be to:
- Either dial back my overall planned pace by about a minute, or do the classic racing no-no of banking time at my original planned pace early, then dialing back the pace for good once the heat becomes noticeable, to minimize my exposure to the worst of the heat.
- String to my running belt my running cap and perhaps a towel/cloth of some kind, for cover. The cap can be wet as needed. I could also pin my bib to my shorts, begin the race with a tech T over my singlet, and remove the T to use as a towel in lieu of a towel.
- Aggressively top the water bottle off before entering the park at mile 20 (32K).
- Absolutely stop and walk/rest through aid stations.
I’m still fairly confident I’ll finish Vancouver as expected. This is all just part of the planning that I was already setting in place for a tough race. But it speaks to a greater point: Don’t underestimate the effect of the heat on your running.